Altered Gene Expression in the Schistosome-Transmitting Snail Biomphalaria glabrata following Exposure to Niclosamide, the Active Ingredient in the Widely Used Molluscicide Bayluscide

In view of the call by the World Health Organization (WHO) for elimination of schistosomiasis as a public health problem by 2025, use of molluscicides in snail control to supplement chemotherapy–based control efforts is likely to increase in the coming years. The mechanisms of action of niclosamide, the active ingredient in the most widely used molluscicides, remain largely unknown. A better understanding of its toxicology at the molecular level will both improve our knowledge of snail biology and may offer valuable insights into the development of better chemical control methods for snails. We used a recently developed Biomphalaria glabrata oligonucleotide microarray (31K features) to investigate the effect of sublethal exposure to niclosamide on the transcriptional responses of the snail B. glabrata relative to untreated snails. Most of the genes highly upregulated following exposure of snails to niclosamide are involved in biotransformation of xenobiotics, including genes encoding cytochrome P450s (CYP), glutathione S-transferases (GST), and drug transporters, notably multi-drug resistance protein (efflux transporter) and solute linked carrier (influx transporter). Niclosamide also induced stress responses. Specifically, six heat shock protein (HSP) genes from three super-families (HSP20, HSP40 and HSP70) were upregulated. Genes encoding ADP-ribosylation factor (ARF), cAMP response element-binding protein (CREB) and coatomer, all of which are involved in vesicle trafficking in the Golgi of mammalian cells, were also upregulated. Lastly, a hemoglobin gene was downregulated, suggesting niclosamide may affect oxygen transport. Our results show that snails mount substantial responses to sublethal concentrations of niclosamide, at least some of which appear to be protective. The topic of how niclosamide’s lethality at higher concentrations is determined requires further study. Given that niclosamide has also been used as an anthelmintic drug for decades and has been found to have activity against several types of cancer, our findings may be of relevance in understanding how both parasites and neoplastic cells respond to this compound.鉴于世界卫生组织（World Health Organization, WHO）呼吁在2025年前消除血吸虫病这一公共卫生问题，未来几年中，在以化疗为基础的血吸虫病防控工作中补充使用杀螺剂进行螺类防控的做法或将增多。目前应用最广泛的杀螺剂的有效成分氯硝柳胺（niclosamide），其作用机制仍未完全阐明。对其分子水平的毒理学进行更深入的研究，既能增进我们对螺类生物学的认知，也可为开发更优质的螺类化学防控方法提供宝贵见解。本研究采用新近开发的光滑双脐螺（Biomphalaria glabrata）寡核苷酸微阵列（包含31K个特征位点），探究了亚致死浓度氯硝柳胺暴露对光滑双脐螺（B. glabrata）转录组的影响，并以未处理的螺类作为对照。经氯硝柳胺暴露后显著上调的多数基因参与异生物质的生物转化过程，包括编码细胞色素P450（cytochrome P450s, CYP）、谷胱甘肽S-转移酶（glutathione S-transferases, GST）以及药物转运蛋白的基因，其中尤为突出的是多药耐药蛋白（外排转运体）与溶质载体家族蛋白（内流转运体）。氯硝柳胺还可诱导应激反应，具体而言，来自HSP20、HSP40和HSP70三个超家族的6个热休克蛋白（heat shock protein, HSP）基因均出现上调。编码ADP核糖基化因子（ADP-ribosylation factor, ARF）、cAMP反应元件结合蛋白（cAMP response element-binding protein, CREB）以及包被蛋白复合体的基因也出现上调，上述基因均参与哺乳动物细胞高尔基体中的囊泡运输过程。此外，一个血红蛋白基因出现下调，提示氯硝柳胺可能会影响螺类的氧运输过程。本研究结果表明，螺类对亚致死浓度的氯硝柳胺会产生显著的应答反应，其中至少部分应答具有保护作用。关于高浓度氯硝柳胺的致死作用机制仍有待进一步研究。鉴于氯硝柳胺已作为抗蠕虫药物使用数十年，且被发现对多种癌症具有抗肿瘤活性，本研究结果或有助于理解寄生虫与肿瘤细胞对该化合物的应答机制。